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Olympic Dam Expansion Draft Environmental Impact Statement 2009 693

23Rehabilitation and closuRe 23

23.1 intRoductionPlanning the closure of the expanded Olympic Dam operation

and its associated infrastructure would be integrated into the

current Olympic Dam Rehabilitation and Closure Mine Plan.

Closure planning was started during the initial planning phase

and would continue to be refined as results from research and

monitoring programs become available, government regulations

and stakeholder expectations change, and technology advances.

The timing of closure for the expanded operation at Olympic

Dam is unknown, although it is likely that the operation would

extend beyond the 40–year timeframe assessed for the Draft

EIS. This chapter presents a proposed closure strategy to

progressively rehabilitate and close the expanded Olympic Dam

operation and its associated infrastructure should the operation

require closure at 40 years. The same overriding principles

would apply at a closure date beyond 40 years, should the

operational life extend. The plan:

identifies the objectives for progressively rehabilitating, •

decommissioning and closing the expanded operation

defines the criteria that would be used to guide and assess •

the achievement of environmental objectives

provides the potential post closure land uses and proposed •

rehabilitation and decommissioning practices for the major

project components

outlines future research and monitoring programs that may •

influence the conceptual closure plan.

23.2 assessment methodsThe conceptual rehabilitation and closure plan described in

this chapter is based on:

BHP Billiton Group’s Closure Standard•

a risk assessment for closure undertaken for the Draft EIS •

(see Appendix C)

the existing Olympic Dam Rehabilitation and Closure Plan•

a rehabilitation and closure study undertaken by Outback •

Ecology Pty Ltd (see Appendix T1 for details).

Rehabilitation practices in the arid zone were reviewed and

discussed with regulatory authorities from South Australia,

Western Australia, Queensland and New South Wales.

The review included site-specific rehabilitation strategies

as well as regulatory guidelines to ensure the approach

proposed for Olympic Dam would meet applicable standards.

The rehabilitation strategies of 22 mining operations in arid

areas that generally receive rainfall of less than 350 mm a year

and have evaporation rates of more than 2,000 mm a year

were considered. A summary of the findings is presented in

this chapter and details provided in Appendix T1.

23.3 existing plan, standaRds and guidelinesThe BHP Billiton Group Closure Standard requires all of its

operations to have closure plans that are reviewed and updated

regularly. The plans are required to identify, mitigate (where

possible), estimate the cost of and manage the current and

future health, safety, environment, community and business

risks associated with closure. The BHP Billiton Group Closure

Standard identifies the following principles for rehabilitation

and closure:

ensure that closure planning is incorporated into the design, •

construction and operation phases

rehabilitate and stabilise disturbed areas as soon as •

reasonably practicable

seek opportunities to reuse/recycle redundant assets during •

operations and on closure

ensure that infrastructure is decommissioned in accordance •

with environmental, health and safety objectives.

Olympic Dam Expansion Draft Environmental Impact Statement 2009694

The Olympic Dam operation’s current rehabilitation and closure

plan was updated recently to comply with the BHP Billiton

Group Closure Standard. The updated plan ensures that the

existing operation complies with statutory, corporate and

site-specific policies, procedures and standards. It states the

objectives of the closure plan, and estimates the cost of

progressive rehabilitation, decommissioning and closure.

The key elements of the plan are to:

integrate closure planning with mine planning and •

budgeting

identify and document the legal requirements and liabilities •

of mine closure

identify the closure requirements and completion criteria •

for each component of the existing operation

present a financial framework, including cost provisioning, •

for rehabilitation and closure of all aspects of the existing

operation

assure the BHP Billiton Group and external parties that •

closure planning and cost provisioning complies with

company and government requirements

present a framework for communication and stakeholder •

consultation, particularly in relation to technical issues

relating to closure and land use objectives

identify the need for further research to guide closure •

planning

identify opportunities for progressive rehabilitation•

identify residual risks associated with closure of the mine •

present a framework for post closure monitoring, auditing •

and reporting.

In accordance with the existing Rehabilitation and Closure

Plan and the United States Sarbanes-Oxley Act 2002 (which

established higher standards for corporate governance and

financial auditing), BHP Billiton would make an accounting

provision each year for the future rehabilitation and closure

of the mine.

South Australian Government regulators are being consulted

about the recently updated Olympic Dam Rehabilitation

and Closure Plan for the existing operation. Guidelines and

standards reviewed during the development of the updated

plan included:

PIRSA Guidelines for Preparation of a Mining Lease Proposal •

or Mining and Rehabilitation Program (PIRSA 2007)

BHP Billiton Group’s Closure Standard•

Australian minerals industry framework for sustainable •

development, particularly the 10 principles of ‘Enduring

Value’ (MCA 2004)

Australian Government Overview of Best Practice •

Environmental Management in Mining (DEH 2002)

Australian and New Zealand Minerals and Energy Council •

Strategic Framework for Mine Closure (ANZMEC 2000)

Western Australia Department of Minerals and Energy •

Guidelines for Mining in Arid Environments (DME 1996)

Code of Practice and Safety Guide for Radiation Protection •

and Radioactive Waste Management in Mining and Mineral

Processing (Australian Radiation Protection and Nuclear

Safety Agency 2005).

23.4 Rehabilitation and closuRe stRategy

23.4.1 bRoad objectives

Although details of land use post closure would be determined

at the appropriate time in the future, the broad objectives of

the closure strategy are to:

ensure that closure planning (including accountability and •

resourcing) is incorporated into the project development,

construction and operation phases

establish a base closure plan that can be reviewed and •

updated during the construction and operation phases

provide information to relevant stakeholders for comment, •

and consider their views during rehabilitation and

decommissioning planning.

Specific closure objectives are to:

comply with applicable BHP Billiton Group, local, state, •

federal and international standards

consult with and address stakeholder concerns•

rehabilitate operational areas to a condition that would •

support post-operational land uses as agreed with

stakeholders

leave operational areas in a state that poses minimal risk •

to the public, native fauna and livestock

ensure public exposure to chemicals and radionuclides is •

within prescribed limits

decommission assets soon after they become redundant•

stabilise and render safe the open pit and waste landforms, •

but leave as features within the landscape

rehabilitate all other disturbed areas•

ensure the visual character of the site is consistent with •

the post-operational use, as agreed with stakeholders

ensure rehabilitated sites and landforms are stable over •

the long term

when possible, restore operational areas to a condition •

that has minimal off-site impact by controlling the release

of pollutants to the air, land and groundwater

rehabilitate operational areas using technically feasible •

and cost-effective methods that avoid ongoing post closure

maintenance

demonstrate that future risks and liabilities associated with •

post closure sites have been eliminated or are controlled

to an acceptable level

reuse assets and recycle materials recovered from •

decommissioned assets where reasonably possible.


23

23.4.2 stakeholdeR involvement

The involvement of stakeholders in developing responsibilities

and agreed closure objectives and outcomes is a critical

component of the rehabilitation and closure planning process.

The process also ensures ongoing consultation and agreement

in accordance with government and community expectations.

The key stakeholders with interests in some or all of the project

components are likely to be:

the Australian Government Department of the Environment, •

Water, Heritage and the Arts (DEWHA)

the South Australian Environment Protection Authority •

(SAEPA)

Primary Industries and Resources South Australia (PIRSA)•

the South Australian Department of Water, Land and •

Biodiversity Conservation (DWLBC)

the South Australian Department for Transport, Energy •

and Infrastructure (DTEI)

other State Government service providers (i.e. health, •

education, law enforcement)

The Northern Territory Department of Natural Resources, •

Environment, The Arts and Sport (NRETAS)

the South Australian Natural Resources Management •

(NRM) Board

the Great Artesian Basin Consultative Committee•

the Pastoral Board •

Roxby Downs and Woomera Community Boards, and •

Andamooka Progress and Opal Miners Association

Flinders and Outback Community Consultative Groups•

non Government Organisations (e.g. South Australian •

Conservation Council)

Roxby Downs Council•

the communities of Roxby Downs, Woomera, Andamooka, •

Marree, William Creek, Port Augusta, Whyalla, Port Pirie

and Darwin.

pastoral communities •

Olympic Dam employees, contractors and suppliers•

Aboriginal groups•

the fishing industry•

Arid Recovery partners (the SA Department for Environment •

and Heritage, the University of Adelaide and the Friends of

Arid Recovery).

Similar to the process followed for developing the current closure

plan, stakeholders would be consulted regularly during the

development of the Olympic Dam Rehabilitation and Closure Plan.

23.5 Rehabilitation and closuRe cRiteRiaClosure criteria are based on the post-operational land use

objectives following consultation with stakeholders. The

progress and success of closure and rehabilitation can be

assessed against these qualitative or quantitative measures.

The current rehabilitation and closure plan details the closure

criteria for the existing operation. These criteria would be

updated to include the expanded mine components when the

detailed plan for the expanded mine is prepared.

Table 23.1 provides a summary of rehabilitation and closure

objectives and the measures against which these objectives

would be assessed.

23.6 design foR closuReMine closure was considered during the design of facilities

for the proposed expansion (see Chapter 5, Description of

the Proposed Expansion). Careful consideration was given

to the layout and design of the mine components so that the

risk of adverse environmental and social impacts after closure

would be minimised. Examples of design considerations

that would assist in improving closure outcomes are:

designs that minimise the footprint of key project •

components by maximising the height of the TSF and RSF;

placing the RSF, TSF and landfill in adjacent locations; and

avoiding the need for additional tailings evaporation ponds

incorporating appropriate safety factors in the designs of the •

TSF and RSF so that long-term physical stability is ensured

careful planning of where potentially reactive rock •

material would be placed in the RSF to ensure that the risks

associated with hazardous leachate, or exposure of reactive

material were minimised.

23.7 pRoject components at yeaR 40The Draft EIS assesses the proposed expansion to Year 40.

It is therefore relevant to consider the status of project

components at Year 40 as an interim stage prior to their final

closure. A conceptual representation of the mine at Year 40

and after final closure is shown in Figure 23.1. Consistent

with the closure strategy, numerous project components would

have been progressively rehabilitated and closed by Year 40.

The status of major project components at Year 40 would be

as follows:

the footprint of the open pit, RSF and TSF would be as •

shown in Figure 23.1

the depth of the open pit would be about 1 km and a lake •

in the base of the pit would not yet have formed

the RSF would have reached its design height, but the haul •

truck access passes would not yet have been re-contoured

the TSF would have reached its design height and some cells •

would have been capped

infrastructure associated with Roxby Downs, Hiltaba Village, •

the airport, rail spur and metallurgical plant would still be

in place.


23.8 outline of pRoposed Rehabilitation and closuRe stRategyRevision of the current Olympic Dam Rehabilitation and

Closure Plan to include the proposed expansion would begin

once the expansion received approval and the detailed design

phase of the project was completed.

This section outlines a conceptual strategy for achieving the

rehabilitation and closure objectives identified in Table 23.1

for each of the main project components. This section focuses

on the high-priority environmental issues.

23.8.1 open pit

The void created by the new open pit mine would remain as

a permanent land feature. As discussed in Chapter 11, Surface

Water, modelling of water into the pit suggests that a lake,

about 100 m deep, would form in the pit about 100–200 years

after closure if the works in the open pit finish at Year 40.

The lake would ultimately reach a depth of about 350 m about

3,000 years after closure. The modelling suggests that there

would be no risk of pit water flowing into and contaminating

regional aquifers. The modelling also suggests the water in the

pit lake would be near neutral (i.e. pH 7.8 eventually reducing

to 7.3), be hyper-saline, and that a gypsum crust would

eventually form over the surface of the lake (about 3,000 years

after closure). The pit water would contain a variety of salts

and a wide range of concentrations of metals (see Section

11.5.4 for details).

During the operation phase of the mine, the quality of water

entering the pit would be monitored regularly so that the

results of the pit hydrology and limnological modelling could

be validated and/or further refined.

It is inevitable that the edges of the pit would gradually erode

and subside. Although the stability of the pit edges after

closure is considered to be low priority from an environmental

perspective, it could affect public safety. Consequently,

geotechnical studies would be conducted during the latter

stages of operation to determine the potential for surface

subsidence around the perimeter of the open pit.

potential post closure land use

The proposed options for how land would be used post closure

include:

vacant crown land, to which access by members of the •

public and livestock would be restricted

a research and education site for geological, environmental •

and engineering disciplines

a managed and regulated tourist attraction.•

table 23.1 summary of closure objectives and performance measures

aspect objective measure

Safety Zero harm to members of the public No preventable injuries or deaths occur

Landform stability The waste landforms (RSF and TSF) remain stable over the long term

Stability of rehabilitated sites is consistent with adjacent terrain

Edges of the open pit are left in a stable condition

No exposure of hazardous materials occurs

No evidence of subsidence around the edge of the open pit at closure

Groundwater Minimise leachate entering the groundwater by covering the TSF and RSF with suitable non-reactive material

Beneficial uses of groundwater and groundwater dependent ecosystems are protected

No mounding of groundwater above 80 m AHD

Yet to be defined, but would be determined in the context of Schedule 2 of the Environment Protection (Water Quality) Policy 2003, and either an attenuation zone, or an amendment to the environmental value of the hyper saline groundwater body beneath Olympic Dam

Terrestrial ecology Minimal risk of contaminated surface water harming fauna (particularly birds)

No adverse effects on fauna (particularly birds)

Soil contamination Soil quality is compatible with final land uses after closure

Schedules B(4), B(5) and B(6) of the National Environment Protection (Assessment of Site Contamination) Measure 1999, relating to effects on human health, ecological receptors and groundwater, respectively

Visual amenity Rehabilitated sites mimic regional terrain

The open pit (which would not be filled) becomes a tourist attraction

None

Dust Dust generation from the closed operation does not cause harm

Comply with OH&S dust limits

Comply with NEPM limits for public exposure

Radiation Exposure to gamma radiation, radionuclides in dust, and radon and its decay products do not cause harm to the public or biota

Comply with OH&S radiation limits (<1 mSv/a to members of the public)

Radiation exposure is consistent with the as low as reasonably achievable (ALARA) principal

Rehabilitation Rehabilitation of operational sites occurs progressively and results in landforms that are consistent with adjacent terrain or the final land use

Rehabilitation of sites occurs as soon as reasonably practical.


23

Figure 23.1 Conceptual representation of the mine at 40 years and post closure

AT 40 YEARS

POST CLOSURE

Rock storagefacility

Openpit

Metallurgicalplant

Tailings storagefacility

HiltabaVillage Airport

RoxbyDowns


It is expected that the South Australian Government would be

responsible for the land, including, if relevant, the maintenance

of viewing platforms and access to the pit by tourists, scientists

and students.

safety

The following measures would be adopted to reduce safety risk

to the public:

geotechnical studies would be conducted during the latter •

stages of the operation to determine the potential for

surface subsidence around the perimeter of the open pit

and to determine the safety exclusion zone

based on these studies, an abandonment bund and/or •

fencing would be constructed around the perimeter of the

pit outside the zone of potential pit-wall subsidence.

This would restrict public access to the edge of the open pit.

Access through the bund to a viewing platform would be

provided if tourism was to be encouraged

access roads and tracks in and around the open pit would •

be ripped to prevent or limit ease of use. One access track

to the viewing platform would be maintained if it was

decided that tourism was to be encouraged

signs warning the public of exposure to radiation and •

possible subsidence would be erected around the edge

of the open pit.

Wildlife

Wildlife, particularly birds, could be attracted to the lake within

the open pit after closure. The lake is not expected to attract

large numbers of birds, however, because the temperature

within the pit would be high (up to 10 °C above ambient),

and the pit lake is unlikely to support aquatic food. Although

the quality of the pit water would be relatively poor (i.e. saline

to eventually hyper-saline), the water quality model indicates

that it would not be toxic to fauna (see Appendix J2).

23.8.2 Rock stoRage facility

The RSF would remain as a permanent landform that would

resemble natural mesas near Coober Pedy and Port Augusta

(see Chapter 20, Visual Amenity).


Potential uses of the RSF post closure include:

vacant Crown land to which public and livestock access •

would be restricted

a managed and regulated tourist attraction, which the •

public would be encouraged to visit

further mining and processing, should metal prices reach •

levels that make it economically viable to recover the low

grade ore stockpiled separately.

stability

The long-term stability of the RSF is essential to ensure the

reactive material is permanently contained within a benign

outer layer. The following measures would be used to minimise

the risk of erosion that may otherwise release reactive material

into the environment (see Chapter 5, Description of the

Proposed Expansion, for details):

no reactive material would be stored under outer slopes•

outer slopes would be constructed using coarse material •

(Class C or D mine rock such as durable sandstone, quartzite

and limestone) that would be resistant to erosion by run-off

and wind

the outermost slopes would be left at their constructed •

slope angles (30– 37°) to minimise the length of slope that

would be susceptible to erosion

the upper surfaces would be covered with a coarse mulch •

layer that is stable and resilient over time and counters the

erosive effects of wind and water. It can be conducive to

plant colonisation through provision of germination niches

and favourable microclimates.

seepage

The RSF would be designed to minimise seepage to, and the

impacts on, groundwater (see Chapter 12, Groundwater).

This would be achieved by:

using non-reactive rock (Class C or D mine rock) to construct •

the outermost walls and covers

using traffic to compact layers, which would reduce the •

infiltration of rainfall into the top of the RSF and movement

of water through the RSF and into the groundwater system

below

including a traffic compacted layer of non-reactive rock •

at the base of the RSF

selectively placing mineralised mine rock (Class A or B •

material) within the RSF to enable potential seepage to

be managed most efficiently.

Radon emanation

The RSF would be designed to ensure that radon emanation

from the facility was consistent with the ‘as low as reasonably

achievable’ (ALARA) principle (see Appendix S). This would be

achieved by:

selectively placing mineralised mine rock (Class A or B •

material) within the RSF to enable it to be most efficiently

enclosed by suitable non-reactive material (Class C or D

material)

enhancing the long-term stability of the facility (as discussed •

above) to ensure that the protective outer layer was not

eroded.


23

safety

The following measures would be implemented at the

RSF to reduce safety risk to the public post closure:

access roads and tracks adjacent to the RSF would be •

ripped to prevent access


possible rock falls would be erected around the edge

of the RSF.

Rehabilitation

The low, unpredictable rainfall at Olympic Dam is the overriding

factor that would influence rehabilitation of the RSF. Local

mesas that generally support little vegetation except in

drainage lines around their bases (see Plate 20.9) provide a

guide to the level of vegetation that may be expected on the

RSF. In light of these limitations, the general rehabilitation

strategy for the RSF would be:

topsoil containing viable seeds of appropriate plants •

associated with the foot-slopes of rocky hills may be used

at strategic locations (e.g. around the base of the RSF)

to promote the natural regeneration of vegetation

seeds of appropriate native (local) species would be spread •

at strategic locations to take advantage of rain events

(see Appendix T2 for details of suitable species). A high

proportion of hard or dormant seeds may be appropriate

so that seeds could survive until favourable rainfall events.

The choice of species would be influenced by soil properties

such as pH, salinity, water retention and plant-available

water (Jasper and Braimbridge 2006)

the steep rocky slopes would be innately resistant to erosion •

and would not require revegetation to enhance stability

establishing nodes of suitable native vegetation on •

5–10% of the top of the RSF may provide a seed source

that would enhance the creation of a self-sustaining system

(see Appendix T2 for details of suitable species)

at some locations, mechanical seeding would be the most •

appropriate technique for applying seed. Mechanical seeders

may be mounted on a bulldozer with a multi-shank ripper

box, enabling a one-pass operation that contour-rips,

seeds and fertilises

dominant local trees such as the Cypress-pine and Mulga •

may be established within depressions, drainage lines or

gullies at the base of batter slopes.

23.8.3 mining facilities and haul tRucks

potential post closure use

Potential uses of the metallurgical plant post closure include

research and education, tourism, and further mineral processing

if the mining of ore from the RSF or TSF occur. If the plant is

decommissioned, the site may revert to stock pasture or

become vacant Crown land. A future use of at least some of the

haul trucks, once decommissioned, may be as a tourist exhibit,

possibly near the open pit.

achieving closure objectives

The potential use of the metallurgical plant for research, as an

educational facility or for tourism, would be investigated prior

to closure. The inclusion of haul trucks as part of the tourist

facility would be considered. If none of these were feasible,

the facilities (including haul trucks) would be decommissioned

and demolished. Reusing the assets and recycling redundant

material would be a priority during decommissioning.

Redundant material would either be removed from the site

by rail (if benign) or buried on-site in an appropriate facility,

i.e. within the RSF, TSF or landfill facilities.

Contaminated soils associated with process ponds and other

work sites would be assessed and remediated as specified

in the amended site contamination provisions (2007) of the

Environment Protection Act 1993, the National Environment

Protection (Assessment of Site Contamination) Measure 1999

(NEPC 1999), and other relevant legislation that addresses

contamination.

All surfaces would be recontoured and deep ripped to

facilitate natural revegetation.

23.8.4 tailings stoRage facility


The TSF would remain as a permanent land feature, resembling

a low mesa to blend in with the surrounding landscape

(see Chapter 20, Visual Amenity). Potential uses of the

TSF post closure include:

further mining, if metal prices reached levels that made •

extraction of the residual metals from the tailings

economically viable

vacant Crown land from which stock would be excluded. •

stability

Tailings are reactive and would, therefore, be indefinitely

encapsulated within erosion resistant earthworks. Design

measures to promote the long-term stability of the TSF would

include (see Chapter 5, Description of the Proposed Expansion,

for details):

armouring the outermost rock on slopes and top surfaces •

with durable rock to protect the slopes from erosion

(preferably limestone or durable sandstone/quartzite)

leaving the outer embankments of the TSF at their angle •

of repose to minimise the length of slope that would be

susceptible to erosion

possibly providing specially armoured sections of the TSF •

wall, such as valley release structures, to accommodate

run-off from extreme storm events

covering the upper surfaces with a coarse mulch layer that •

is stable and resilient over time and counters the erosive

effects of wind and water.


seepage

Tailings associated with the proposed mine expansion would be

expected to have similar properties to those currently produced

at Olympic Dam. The tailings contain 70–80% of the radioactive

material associated with the original ore. The tailings liquor is

acidic and contains dissolved metals (including copper and

uranium). Groundwater monitoring associated with the existing

TSF has demonstrated that the calcareous clays and limestone

beneath the facility neutralise the tailings seepage to a large

extent, resulting in a large proportion of the metals

precipitating and becoming immobile (see Chapter 12,

Groundwater). Natural attenuation would continue to occur

post closure.

Management measures adopted in the design of the TSF to

minimise seepage are discussed in Chapters 5, Description of

the Proposed Expansion; 12, Groundwater, and Appendix F1.

The following measures would be adopted to minimise potential

seepage into groundwater from the TSF post closure:

tailings cells would be capped when they reached their •

target design height, and when it was safe for vehicles

to access the TSF surface (i.e. when the tailings are

sufficiently dry)

rainfall infiltration into the tailings would be minimised •

by constructing a low permeability capping layer

the most suitable cover would be defined by future test •

work.

Radon emanation

Monitoring radon and radon decay products on and adjacent to

the existing TSF has shown that radon is dispersed and diluted

by local air movement to very low levels within a short distance

(WMC 2004). Similar dispersion and dilution of radon would be

expected with the expanded TSF. Nevertheless, the following

measures would be implemented to minimise radon emanation

after closure:

the surface of the TSF would be capped with sufficiently •

thick benign material (nominally 0.5 to 1.5 m, depending

on the type material)

the cap would be covered with a layer of coarse rocky •

material to ensure it resisted erosion by wind and water

the details of the most suitable cap would be defined by •

future test work, when volumes of rock were available

from the open pit.

safety

The following measures would be implemented at the TSF

to reduce safety risk to the public post closure:

the facility would be capped with sufficiently thick benign •

material to minimise the potential exposure of the public

to acidic liquor and radiation

access roads and tracks adjacent to the TSF would be •

ripped to restrict access

a fence would be constructed around the base of the •

TSF to prevent vehicle and stock access


possible rock falls would be erected around the edge of

the TSF.

dust

Dust emissions from the surface of the TSF would be minimised

by an outer layer of rock armouring. The proposed cap for the

TSF would probably consist of a low-permeability layer on top

of the facility. This layer would be further defined through

future test work. The cap would be covered with a layer of

coarse rocky material to ensure it resisted erosion by wind and

water. The surface would be similar to the natural gibber plains

that are highly resistant to erosion.

Vegetation would not be established on the TSF surface to

further minimise dust emissions because there is a possibility

it would take up metals (see below for details).

metal uptake by vegetation

After closure, vegetation growing on the TSF may take up

metals, which would expose native fauna and stock to risk

when grazing (SRK Consulting 2005). The degree of metal

uptake depends on the extent of root penetration into the

TSF surface, and the concentration of metals in the root zone

of plants. This may be alleviated somewhat by high metal

concentrations being accompanied by high salt concentrations,

which would tend to discourage root growth and, as a

consequence, restrict metal uptake (Golder Associates 2003;

SRK Consulting 2005).

The risk of vegetation taking up metals would be minimised by

discouraging vegetation regrowth on the TSF through creating

a surface on the TSF that is not conducive to plant growth.

Rehabilitation

The early concept of rehabilitating the existing TSF at

Olympic Dam was to establish a gibber-type tableland, with

the surface covered in a grassland and chenopod-dominated

shrubland and the walls covered with chenopod shrubland with

occasional low woodland species (Kinhill 1997). As discussed

above, subsequent studies have suggested that establishing

vegetation on the TSF is inappropriate due to the potential for

the vegetation to take up metals. It is more likely, therefore,

that revegetation of the TSF surface would be discouraged.

A detailed rehabilitation plan for the TSF would be developed

when the design of its cover had been completed. Conceptual

designs are provided in Appendix F1, and include the following.

the most appropriate form of rehabilitating the TSF would •

be investigated further during the operation phase when

research trials and performance monitoring would occur.

Suitable materials for use in rehabilitation would be defined

and stockpiled, if necessary, as mining progressed.

the TSF cells would be rehabilitated as each cell reached •

the end of its operational life. This would manage dust,

surface water and radon emanation.


23

final rehabilitation plans would be prepared during the •

lead-up to closure, as large quantities of mine rock would

be available to construct the features required to manage

environmental risks associated with closure.

23.8.5 Roxby doWns, olympic dam village

and aiRpoRt


The use of land post closure would be determined by consulting

with relevant stakeholders, including the local government

authority, the Roxby Downs and Andamooka communities and

the South Australian Government. Olympic Dam Village and the

existing airport would ultimately be covered by the RSF. The

new airport would probably be wholly-owned by BHP Billiton,

and post closure land use would be determined in consultation

with the above stakeholders.

Roxby Downs and the new airport may be used as a regional

centre for research, education, tourism and mining, or a

combination of all of these. If the town and new airport were

no longer viable, the land would be used for stock pasture or

as vacant Crown land.


When Olympic Dam Village and the existing airport are

decommissioned and relocated during the operation phase,

reusing as much of the infrastructure as possible when

developing the new Hiltaba Village, heavy industrial area

and the new airport would be a high priority.

The potential use of Roxby Downs and the new airport would

be investigated prior to closure of the mine. If the town was

economically viable without the mine, much of the existing

infrastructure within the town and the airport would continue

to be used.

If the town was not economically viable after closure of the

mine, however, the infrastructure owned by BHP Billiton,

including components of the town and airport, would be

decommissioned and removed. Reuse of the infrastructure

wherever possible at other regional centres such as

Andamooka, Woomera or Coober Pedy would be a priority.

Surfaces would be re-contoured, deep ripped and revegetated.

23.8.6 hiltaba village


Hiltaba Village could be used for accommodation, research

laboratories and as education and/or training facilities post

closure. If decommissioned, however, the site would revert

to pastoral use.


At mine closure, as much of the Hiltaba Village infrastructure

as possible would be sold and reused and/or recycled in and

around Roxby Downs, Andamooka and regional centres.

All redundant material would either be removed from the site

or buried at Olympic Dam in an appropriate facility. Surfaces

would be re-contoured and deep ripped to facilitate natural

revegetation.

23.8.7 desalination plant


The desalination plant could continue to supply potable water

to the Eyre Peninsula, the Upper Spencer Gulf region and other

areas. As a modular construction method would be used,

part of the desalination plant could be decommissioned if the

demand for water was less than its full capacity. If it was fully

decommissioned, the site would become available for other

industrial uses if it remained zoned as industrial land.


At mine closure, alternative markets would be investigated

for the water produced at the desalination plant. These may

include Whyalla, Port Augusta and Port Pirie. If the desalination

plant was partly or fully decommissioned, as much of the

infrastructure as possible would be sold and/or reused.

All redundant material would be removed from the site and

disposed of at a licenced landfill site. If no further industrial

use occurred, surfaces would be re-contoured and deep ripped

to facilitate natural revegetation. Buried infrastructure, such

as the intake and outfall pipelines, would remain in the

ground or under the seabed.

23.8.8 WateR supply pipelines


The water supply pipelines include the existing pipes from the

Great Artesian Basin (GAB) to Olympic Dam, and the proposed

water supply pipeline from the Point Lowly desalination plant to

Olympic Dam. The latter may continue to be used to supply

water to regional centres in northern South Australia, but it is

less likely that the lines from the GAB wellfields would continue

to be used.

Decommissioned pipeline easements would revert to

pastoral use.


Prior to mine closure, future use of the water pipelines would

be investigated. If none was identified, the pipelines would be

decommissioned. All above ground infrastructure would be

removed and recycled, or removed to an appropriate landfill

site. Buried infrastructure would remain in the ground.


23.8.9 Wellfields


The Great Artesian Basin (GAB) and Motherwell wellfields

include numerous groundwater wells and associated diesel

pumps. Although some of the GAB wells may continue to be

used to supply water for stock, it is less likely that any of the

Motherwell wells would continue to be used as the water is

very saline. Wells would be decommissioned in accordance

with Department of Water, Land and Biodiversity Conservation

(DWLBC) licence conditions.


Prior to mine closure, future use of the wellfields by local

pastoralists or other mining ventures in the region would be

investigated. If none was identified, the wells would be plugged

with concrete and abandoned. All above ground infrastructure

would be removed and recycled or removed to an appropriate

landfill site. Buried infrastructure would remain in the ground.

23.8.10 eneRgy infRastRuctuRe


Post closure, the power station, gas supply pipeline and

transmission lines could continue to supply electricity to

industries and towns in northern South Australia, or could

convey electricity (possibly even from future geothermal or

solar sources) to the NEM. If decommissioned, the power

station site and transmission line and gas pipeline easements

would revert to existing land uses, which may include

pastoral land use or conservation.


Before the mine closes, alternative uses for the power station,

gas supply pipeline and transmission lines would be

investigated. If none were identified, the infrastructure would

be decommissioned. The power station and transmission line

infrastructure would be dismantled and reused or recycled.

All above ground infrastructure associated with the gas pipeline

would be removed and recycled or disposed of in an appropriate

landfill site. Buried infrastructure would remain in the ground.

All infrastructure sites would be recontoured and access tracks

ripped and revegetated.

23.8.11 Rail line


The rail spur to Olympic Dam could continue to be used for

goods/tourist transport to Roxby Downs and Woomera. If it was

to be decommissioned, it would be one of the last infrastructure

components removed as it would be used to transport other

benign and redundant materials from the closed Olympic Dam

operation. The rail easement would ultimately revert to

pastoral land use.


Prior to mine closure, future use of the rail line would be

investigated. If none was identified the rail line would be

decommissioned, and all infrastructure removed and recycled

or removed to an appropriate landfill site. The rail

embankments would be ripped and revegetated.

23.8.12 poRt and landing facilities


The port facilities at Port Adelaide, Outer Harbor and the

Port of Darwin would probably continue to be used as port

facilities and/or as industrial sites by other commercial

enterprises. Similarly, the landing facility may continue to

be used as a landing for future mining or other enterprises

in the region. Alternatively, the pier may be transferred to

the South Australian Government for use by the public.


Prior to mine closure, future uses of the port and landing

facilities would be investigated.

At the Port of Darwin, one important component of closure

would be to investigate radionuclide contamination at the site,

and take measures during rehabilitation, if necessary, to ensure

that potential public exposure to radionuclides were within

prescribed limits.

If no future uses for the port and landing facilities were

identified, the facilities would be decommissioned. All

infrastructure would be removed and recycled, or removed to

an appropriate landfill site. The sites would be rehabilitated

to a condition consistent with post-operational land uses,

as agreed with stakeholders.

23.8.13 undeRgRound opeRation


It is most likely that the open pit mine would extend beyond

the 40–year life assessed in the Draft EIS and progressively

mine out the underground operation.


Prior to mine closure, future uses for the underground facilities

would be investigated. If none were identified, the underground

facilities would be decommissioned. The existing Closure Plan

for Olympic Dam describes in detail how the underground

facilities would be decommissioned. The main elements of

the plan are as follows:

subsidence risks would be investigated and addressed, •

if deemed necessary, by backfilling high-risk shafts with

cemented aggregate fill (CAF)

all surface infrastructure would be removed and recycled, •

or removed to an appropriate landfill site

all underground infrastructure would be removed if •

recyclable, or left in situ

the Whenan shaft, portals and raise bores would be sealed •

with pre-cast concrete

soil would be mounded over the concrete seals•

the site would be recontoured to reinstate natural contours •

and drainage lines, deep-ripped and allowed to naturally

revegetate.


23

23.9 Rehabilitation and closuRe pRocesses

23.9.1 mateRials management

mine rock

The physical and geochemical properties of the rock materials

that would be generated during the mining operations were

characterised as part of mine planning. Cores were analysed in

a comprehensive drilling program, and a mine plan that achieved

the selective placement of Class A to D material was developed

(see Chapter 5, Description of the Proposed Expansion).

The waste properties that determine rehabilitation strategies

include acidity, salinity, sodicity, erodibility, particle size

distribution, strength, water-holding capacity and hydraulic

conductivity, acid-generating potential, and nutrient and metal

availability (Jasper and Braimbridge 2006). Mine rock would be

placed in the RSF according to:

chemical toxicity (e.g. acid-formation, excess metal •

availability, salinity)

susceptibility to erosion (e.g. particle size distribution, •

structural stability, sodicity)

capacity to support plant growth (e.g. soil permeability, •

ability to retain water, nutrients).

The rehabilitation plans for the RSF and TSF would be updated

as more information about the characteristics of the mine rock

was gathered during the operation phase of the mine.

topsoil and vegetation

A management plan would be prepared to guide the reuse of

topsoil (including sand) and cleared vegetation at sites where

revegetation was an appropriate rehabilitation objective.

Topsoil and cleared vegetation would be managed as follows:

opportunities for topsoil and vegetation to be stripped •

and immediately respread on rehabilitated surfaces, or

stockpiled as close as possible to the site where they would

be respread, would be investigated as the mine plan was

refined, and implemented where practicable

vegetation would be spread over the surfaces of topsoil •

stockpiles to provide surface protection and a seed source.

Regrowth of vegetation on stockpiles would be encouraged

topsoil stockpiles (planned for reuse within 1–2 years) would •

be designed to harvest rainfall and encourage continued

biological activity within the soil; as such they would be

as low as possible (with a target height of about 1 m)

harvested topsoil and vegetation would be reused as soon •

as possible after stockpiling

where large volumes of topsoil have to be stockpiled, •

and reuse within 1–2 years is not feasible, stockpiles would

be higher than 1 m to reduce the area of stockpiles to

a practical size. Before reuse, such topsoil would require

the addition of seed and fertiliser as some degree of soil

sterilisation would inevitably have occurred during stockpiling.

23.9.2 Revegetation

surface and soil preparation

The success of revegetation would be significantly enhanced

if the soil surface was prepared appropriately, particularly in

relation to water and nutrient harvesting, and the trapping of

seed. Treatment of soil surfaces used to promote vegetation

growth would include:

the removal of soil compaction by ripping with winged •

ripping tynes, or cultivating with tyned instruments or

scalloped discs on flatter areas with lighter, deeper soils

respreading topsoil evenly over the disturbed area to a •

depth of 5–10 cm

respreading cleared vegetation over disturbed surfaces. •

Reconstruction of soil profiles

Reconstruction of appropriate soil profiles to support

regrowth of native vegetation would be an important part of

rehabilitation at some sites affected by the mine expansion.

At sites where wastes hostile to plant growth may be covered,

reconstruction of a soil profile would include topsoil (5–10 cm),

and benign mine rock from the cover sequence, which would be

used to form a growth medium to accommodate root growth

and store water.

seed and seedling stock

Large quantities of high quality native seed would be

required to help rehabilitate particular mining and residential

development sites. Suitable species would be those with seeds

that could be collected in large quantities, were relatively

straightforward to process and store, had defined treatments

for dormancy release, and were recognised as coloniser species

or generalists. Techniques for seed collection, treatment and

storage are outlined in Appendix T1. A list of plant species that

may be important in re-establishing vegetation on disturbed

areas at Olympic Dam is included in Appendix T2.

BHP Billiton would work closely with suitable contractors to

establish a seed collection, treatment and storage program

to support rehabilitation initiatives at Olympic Dam. One aim

of the program would be to ensure that contractors acquired

and stored sufficient native seed during favourable seasons.

Large quantities of native tube stock would also be required to

provide selected species for planting in high value areas such

as Roxby Downs.

BHP Billiton would support the Australian Arid Lands Botanic

Gardens at Port Augusta to manage the provision of both native

seed and tube stock for rehabilitation and revegetation

programs at Olympic Dam.


Revegetation techniques

In most cases, disturbed areas would be allowed to revegetate

naturally, although in some areas direct intervention to promote

revegetation would be needed. The methods used would

include the following:

mechanical seeders would be used to apply seed to large •

areas of freshly ripped material, with hand seeding for

small areas

tube stock may be used for vegetation establishment on •

a small scale in areas of high importance such as Roxby

Downs, or where it was necessary to establish rare flora

species that were difficult to establish from direct seeding

fauna habitat would be created as appropriate in •

rehabilitated areas, using rocks or vegetation debris

the presence of weeds at rehabilitated sites would be •

monitored by environmental staff or suitable contractors.

If they were found, control measures would be implemented

if grazing was adversely affecting revegetation, its impact •

on rehabilitation would be minimised by fencing

rehabilitated areas temporarily.

23.9.3 contaminated land

Rehabilitation of contaminated land would be consistent

with the National Environment Protection (Assessment of Site

Contamination) Measure 1999. Accordingly, a tier based

assessment of risks associated with contaminated land would

be undertaken to screen potential risks to human health,

ecological receptors and groundwater. The outcomes of the

risk assessment would determine the most appropriate level

and type of rehabilitation of contaminated sites. Rehabilitation

approaches would be likely to include removal of contaminated

soil to an appropriate treatment and disposal facility, in situ

treatment, burying and capping on-site, encapsulating in an

engineered cell, or do-nothing, depending on the assessed

level of risk.

23.10 closuRe costsClosure cost estimates for the major project components are

being developed within the economic model for the mine

expansion. Demolition costs were assumed to be a percentage

of the capital construction costs (often 10%, but ranging from

about 2% to 20% depending on the item).

In developing the closure costs, it was assumed that mine

closure costs would be incurred for demolition and

rehabilitation activities scheduled to commence immediately

after mining stopped. Demolition and rehabilitation

activities that take place throughout the mining operation

(e.g. progressive tailing rehabilitation) were considered as

an operational cost.

More detailed cost estimates would be developed as part of the

Closure Plan that would be produced if the mine expansion was

approved. The closure costs would be reviewed regularly during

the life-of-mine.

BHP Billiton would make an accounting provision each year for

the future rehabilitation and closure of the mine.

23.11 Risk assessment foR closuReRisks associated with closure were assessed according to the

BHP Billiton Group Risk Management Standards. A risk register

was developed, reviewed and validated (see Chapter 26, Hazard

and Risk and Appendix C). The assessment identified controls

and responsibilities to prevent or mitigate each risk event and

produced a residual risk rating for each risk event. The level of

each closure risk was considered to be acceptable.

The most significant post closure risk identified during the risk

assessment was the failure (via erosion) of the RSF and TSF

side walls and cover such that reactive material was carried by

run-off into the surrounding environment. BHP Billiton would

therefore investigate, design, build and maintain structures that

would contain reactive material indefinitely and have the least

likelihood of failure. The risk would be reduced by ensuring that

rehabilitation of disturbed areas and waste landforms occurred

progressively, thereby ensuring stability, and control of

emissions to the air and land.

Risk assessment for closure would be an ongoing process during

the operational life of the project.

23.12 monitoRing and ReseaRchThe Olympic Dam Rehabilitation and Closure Plan is updated

regularly to ensure that the proposed practices are consistent

with the most up-to-date knowledge and technologies. All

operations of the BHP Billiton Group are committed to continual

improvement through an ongoing program of monitoring and

research in closure technologies and leading practices.

The following sections outline the monitoring and research

areas that would occur during the operation phase of the

expanded Olympic Dam mine and provide additional

information to help refine the rehabilitation and closure plan.

The projects below would be incorporated into the Olympic Dam

environmental management plans as discussed in Chapter 24,

Environmental Management Framework.

23.12.1 pit WateR quality and quantity

The quantity and quality of water entering the pit during the

operation phase of the mine would be monitored regularly.

This data would enable the results of the modelling to be

refined, resulting in refined predictions about the quantity

and quality of pit water after the mine had been closed

(see Chapter 11, Surface Water for details).


23

23.12.2 Rock stoRage facility and tailings stoRage

facility Rehabilitation tRials

During the first five to 10 years of the mine expansion,

BHP Billiton would undertake trials to determine the optimal

surface and slope designs for the waste landforms to ensure that:

the landforms resisted erosion and reactive material •

remained enclosed permanently

emission of radon gas to the atmosphere were consistent •

with the ‘as low as reasonably achievable’ (ALARA) principle

(see Chapter 22, Health and Safety and Appendix S)

infiltration and attenuation of contaminated leachate •

into the groundwater, or from the toe of the landforms,

was minimised.

23.12.3 optimising Revegetation and Rehabilitation

A revegetation research program would be developed as part of

the overall rehabilitation plan for the Olympic Dam operation.

It is anticipated that the research program would include

investigating the suitability of particular species for specific

revegetation purposes and soil treatment strategies to promote

revegetation across the mining lease.

Areas of the SML, such as sections of the RSF outer walls,

would be made available during the early years of the mine

expansion to refine vegetation establishment techniques

and quantify plant performance.

23.12.4 metal uptake by vegetation

In the longer term, it is inevitable that vegetation would

re-establish on the waste landforms, either naturally, or

through active revegetation programs. The potential for

uptake of metals by vegetation growing on the TSF is currently

unknown because none of the existing facilities have been

decommissioned and rehabilitated. Part of the landform surface

trials discussed earlier would be to investigate the potential

uptake of metals by vegetation growing on the landforms.

A section of each of the trial landform surfaces would be

revegetated with a range of endemic plant species, including

deep-rooted woody shrubs. Controls would consist of the same

plant species growing on identical surface material placed over

benign rock. Metal levels within the plant leaves and fruit

would be monitored over the course of the trial.

23.12.5 long-teRm monitoRing

Monitoring programs, using appropriate criteria or indicators,

would be established during the operation phase of the mine

to determine whether closure criteria had reached for sites that

were being progressively rehabilitated. The monitoring program

would include assessing:

the stability of the RSF and TSF•

groundwater quality in the vicinity of the RSF and TSF•

dust and radon emissions from the RSF and TSF•

the performance of constructed surfaces in terms of •

water storage and deep percolation of incidental rainfall

properties of the soil in relation to requirements for •

plant growth

the structural attributes of the plant community •

the composition of the plant community •

selected indicators of ecosystem functioning.•

The long life-of-mine at Olympic Dam provides the opportunity

to monitor rehabilitated sites and assess the suitability and

performance of rehabilitation techniques for sites such as the

RSF and TSF. It is envisaged that ongoing monitoring of

rehabilitation successes and failures at Olympic Dam would

enable rehabilitation techniques to be refined and improved

throughout the life-of-mine. It is assumed that, by the end of

the mine’s life, rehabilitation techniques would have been

refined to such a point that achieving the closure criteria would

be a routine occurrence. Post closure monitoring would

therefore focus on assessing the achievement of the agreed

closure criteria. In particular, monitoring of post mining impacts

on beneficial uses of groundwater in the region would continue

for an appropriate period to ensure that users of groundwater

were protected from potential adverse effects.

Progress would be routinely audited and reported to

government authorities in the annual environmental reports,

as is currently the case.

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